This proposal is a collaborative R01 submitted by Duke University, the University of Texas Southwestern Medical Center, and the University of Texas at Arlington. We plan to further develop and evaluate the 30-item Inventory of Depressive Symptomatology, which is available in clinician-rated (IDS30) and self-reported (IDS-SR30) forms, and to further develop and evaluate a shortened version (the Quick IDS), which is available in a 16-item self-report (QIDS-SR16) and a clinician-rated (QIDS-C16) format. The properties of each of these four instruments as both screens for depression in general medical and psychiatric populations, and as measures of symptomatic change will be evaluated. We will analyze data that have been or that are now being collected from "ongoing" studies. We will also acquire and analyze new data from "prospective" studies to be conducted at Duke and at UT Southwestern. These studies will evaluate the performance of each measure to screen for major and minor depression, defined by a structured interview to render DSM-IV diagnoses - DIS (elderly), by SCID (adults), or by the K-SADS-PL (children/adolescents). We will evaluate concurrent validity with the Montgomery Asberg Depression Rating Scale (MADRS), the 17-item Hamilton Depression Rating Scale (HRSD17), or Children's Depression Rating Scale (CDRS) as outcome measures in adolescent, adult, and older/elderly populations. Classic psychometric properties (e.g., factor analyses, Cronbach's alpha, concurrent validity) will be established for each of these four measures (IDS-SR30, IDS-C30, QIDS-SR16, QIDS-C16). We will determine whether an anxiety subscale of the IDS-C or IDS-SR can be identified and compare the potential items against the Spielberger State Anxiety Inventory. We will create equivalence tables using Item Response Theory analysis to translate total scores on the IDS or QIDS to total scores on the HRSD17, MADRS, and CDRS. We will provide benchmark scores for depressive symptom severity by IDS/QIDS ratings to identify minimal, mild, moderate, and severe levels of impaired daily function, as measured by the Sheehan Disability Scale (DIS), SF-12, SF-36, or Social Adjustment Scale-Self-Report (SAS-SR). The result will be a matched self-report and clinician rating scale to assess only the core criterion symptoms of major depression (i.e., the QIDS-C and SR), and more expanded scales capable of assessing both core and associated symptoms (e.g., anxiety, irritability) (IDS-C and SR) that are in the public domain for use with patients across the age spans seen in practice and in research.